If you read through the procedure and look at the images that accompany the steps, you will see that where the measuring cup is used, it shows a 1-cup measuring cup. You are told to "Scoop one cup of baking soda".... you could use a different size measuring cup, as long as you use the correct total amount.
Please note that this STEM activity is not recommended for a science fair project. Be sure that you have your teacher's approval, if required, for your project.
See this note on the activity:
"This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation."